Copying data from multiple point-in-time copies to a log storage to use to roll-back a source storage

ABSTRACT

Provided are a computer program product, system, and method for copying data from multiple point-in-time copies to a log storage to use to roll-back a source storage managing point-in-time copies of a source storage. A plurality of point-in-time copies of a source storage at different point-in-times are established. In response to receiving writes to the source storage after establishing each of the point-in-time copies, point-in-time data in the source storage is copied, before being updated by the received writes, to a log storage, wherein the log storage stores point-in-time data for multiple of the point-in-time copies. The log storage is used to roll-back the source storage to a selected point-in-time of one of the point-in-time copies.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a computer program product, system, andmethod for copying data from multiple point-in-time copies to a logstorage to use to roll-back a source storage.

2. Description of the Related Art

In a storage environment, a storage controller may create point-in-time(“PiT”) copies of a production volume using point-in-time copytechniques, such as the IBM FlashCopy® (FlashCopy is a registeredtrademark of IBM), snapshot, etc. A point-in-time copy replicates datain a manner that appears instantaneous and allows a host to continueaccessing the source volume while actual data transfers to the copyvolume are deferred to a later time. The point-in-time copy appearsinstantaneous because complete is returned to the copy operation inresponse to generating the relationship data structures without copyingthe data from the source to the target volumes. Point-in-time copytechniques typically defer the transfer of the data in the source volumeat the time the point-in-time copy relationship was established to thecopy target volume until a write operation is requested to that datablock on the source volume. Data transfers may also proceed as abackground copy process with minimal impact on system performance. Thepoint-in-time copy relationships that are immediately established inresponse to the point-in-time copy command include a bitmap or otherdata structure indicating the location of blocks in the volume at eitherthe source volume or the copy volume. The point-in-time copy comprisesthe combination of the data in the source volume and the data to beoverwritten by the updates transferred to the target volume.

When an update to a block in the source volume involved in apoint-in-time copy relationship is received, the copy of the track as ofthe point-in-time must be copied to a side file or the target volumebefore the new data for the track is written to the source volume,overwriting the point-in-time copy of the data.

If the data in the source volume becomes corrupted or invalid, thatcorruption is also mirrored to the mirror copy, which may comprise apoint-in-time copy, such that both versions of the data have beencorrupted at this point. The point-in-time copies may be used asrecovery points to try to recover the source volume to a point where thedata has no corruption. However, it can be cost prohibitive to maintainnumerous point-in-time copies to allow recovery to a closestpoint-in-time where there was valid data prior to being corrupted.

SUMMARY

Provided are a computer program product, system, and method for copyingdata from multiple point-in-time copies to a log storage to use toroll-back a source storage managing point-in-time copies of a sourcestorage. A plurality of point-in-time copies of a source storage atdifferent point-in-times are established. In response to receivingwrites to the source storage after establishing each of thepoint-in-time copies, point-in-time data in the source storage iscopied, before being updated by the received writes, to a log storage,wherein the log storage stores point-in-time data for multiple of thepoint-in-time copies. The log storage is used to roll-back the sourcestorage to a selected point-in-time of one of the point-in-time copies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a storage environment.

FIG. 2 illustrates an embodiment of point-in-time copy information.

FIG. 3 illustrates an embodiment of a log entry in log storage.

FIG. 4 illustrates an embodiment of an entry in recovery metadata.

FIG. 5 illustrates an embodiment of operations to generate apoint-in-time copy of a source storage.

FIG. 6 illustrates an embodiment of operations to process a write to thesource storage while there is an active point-in-time copy.

FIG. 7 illustrates an embodiment of operations to roll-back the sourcestorage to a previous point-in-time.

FIG. 8 illustrates an embodiment of operations to iteratively performroll-back operations to a previous point-in-time having valid data.

FIG. 9 illustrates a computing environment in which the components ofFIG. 1 may be implemented.

DETAILED DESCRIPTION

Described embodiments provide techniques for maintaining information onpoint-in-time data for different point-in-time copies of sourcestorages, such as volumes, that may be used to roll-back the sourcevolume to a previous point-in-time of a point-in-time copy. Thedescribed embodiments may be used to form recovery volumes comprisingthe data for the source volume as of a previous point-in-time of one ofthe point-in-time copies that has valid data in the event the sourcevolume has corrupted or invalid data.

In described embodiments, point-in-time data from a source storage foran active point-in-time copy is copied to a log storage, which storespoint-in-time data for multiple of the point-in-time copies when theyare active. The log storage may be used to roll-back the source storageto a selected point-in-time of one of the point-in-time copies.

FIG. 1 illustrates an embodiment of a data storage environment having astorage controller 100 managing access to a source storage 102 thatincludes source volumes 104 _(i), such as a production volume used bydifferent host systems 106, and a target storage 108. The volumes 104_(i) may be comprised of extents 110 of contiguous tracks. A host system106 includes a point-in-time copy manager program 112 to establishpoint-in-time copies at the storage controller 100, such as FlashCopy,snapshot, etc. The storage controller 100 and hosts 106 may communicateover a network 114.

The storage controller 100 includes a point-in-time copy manager 116 tocreate point-in-time copies of data in the source storage 102, e.g.,FlashCopy, snapshot, etc. When creating a point-in-time copy, thepoint-in-time copy manager 116 generates point-in-time copy information200 on the point-in-time copy created as of a point-in-time. The storagecontroller 100 further includes an operating system 118, including thecode and logic to manage Input/Output (“I/O”) requests to the sourcestorage 102. The operating system 118 may configure the source storage102 and target storage 108 in one or more volumes 104 _(i) and data,such as tracks or logical block addresses (LBAs), grouped in extents.Extents 110 may comprise any grouping of tracks or data units instorage. The point-in-time copy manager 116 may be a copy servicesupplied with the operating system 118.

When a storage location, such as a track, in a source storage, e.g.,volume, in an active point-in-time copy relationship identified in thepoint-in-time copy information 200, is subject to a write request, thepoint-in-time copy manager 116 copies the current data at the track,referred to as the point-in-time data, to a log storage 300 in thetarget storage 108. Only after copying the point-in-time data to the logstorage 300 may the write data be applied to the source storage 102location, so that the log storage preserves the point-in-time data forthat source storage location. The point-in-time copy manager 116 maymaintain a log storage pointer 120 that addresses a next location in thelog storage 300 at which to write point-in-time data about to beupdated. In certain embodiments, the log storage 300 may sequentiallystore point-in-time data across multiple point-in-time copy 200relationships.

A recovery manager 122 may perform a recovery operation to roll-back thedata in the source storage 102 to a point-in-time of one of thepoint-in-time copies 200. The recovery manager 122 may use recoverymetadata 400 that provides information on point-in-time data in the logstorage 300 for point-in-time copies 200. The recovery manager 122 maygenerate a recovery point-in-time copy 200 _(R) to reconstruct data fromthe log storage 300 for a point-in-time at which to restore or roll-backthe source storage 102. The recovery manager 122 may store point-in-timedata for a recovery point-in-time copy 200 _(R) in a recovery volume 130in the target storage 108, as opposed to the log storage 300.

The storages 102 and 108 may comprise different types or classes ofstorage devices, such as magnetic hard disk drives, solid state storagedevice (SSD) comprised of solid state electronics, EEPROM (ElectricallyErasable Programmable Read-Only Memory), flash memory, flash disk,Random Access Memory (RAM) drive, storage-class memory (SCM), etc.,Phase Change Memory (PCM), resistive random access memory (RRAM), spintransfer torque memory (STM-RAM), conductive bridging RAM (CBRAM),magnetic hard disk drive, optical disk, tape, etc. The volumes 104 anlog storage 300 may further be configured from an array of devices, suchas Just a Bunch of Disks (JBOD), Direct Access Storage Device (DASD),Redundant Array of Independent Disks (RAID) array, virtualizationdevice, etc. Further, the storages 102 and 108 may compriseheterogeneous storage devices from different vendors and different typesof storage devices, such as a first type of storage devices, e.g., harddisk drives, that have a slower data transfer rate than a second type ofstorage devices, e.g., SSDs.

The network 114 may comprise a network such as one or moreinterconnected Local Area Networks (LAN), Storage Area Networks (SAN),Wide Area Network (WAN), peer-to-peer network, wireless network, etc.

The point-in-time copy manager 116 performs a point-in-time copyoperation that creates a copy of specified extents in a manner thatappears instantaneous and allows a process to continue accessing theextents subject to the point-in-time copy while actual data transfers ofthe copied data are deferred to a later time. The point-in-time copyappears instantaneous because complete is returned to the copy operationin response to generating the relationship data structures, such as thepoint-in-time copy information 200 and change recording information,without copying the data.

In FIG. 1, the point-in-time copy managers 112, 116 and recovery manager122 are shown as implemented in separate computing systems, a host 106and storage controller 100. In alternative embodiments, thepoint-in-time copy managers 112, 116 and recovery manager 122 may beimplemented on a same computer system and operating system. Stillfurther, the point-in-time copy managers 112, 116 and recovery manager122 may be modules within a single deployed computer program installedon a single computer system/operating system.

FIG. 2 illustrates an instance of the point-in-time copy information 200_(i) in the point-in-time copy information 200, also referred to as apoint-in-time copy, and may include: a point-in-time copy identifier 202providing a unique identifier of a point-in-time copy; a source storage204 indicating a division of storage subject to a point-in-time copyoperation, such as a volume, data set, range of extents, etc.; a targetstorage 206 indicating where the point-in-time data is copied, which maycomprise the log storage 300, a recovery volume 130, or other location;a point-in-time 208 of the point-in-time copy 202, such that data in thesource storage 204 for the point-in-time copy 200 _(i) is consistent asof that point-in-time 208; change recording information 210 indicatingwhich data or tracks in the source storage 204 has changed since thepoint-in-time 208, which may comprise a bitmap having a bit for eachdata unit (e.g., track) that is set to one of two values indicating thedata or track represented by the bit has or has not been updated sincethe point-in-time 208; and an active status 212 indicating whether thepoint-in-time copy 202 is active and still recording changes made to thesource storage 204. The point-in-time copy managers 112, 116 maygenerate numerous point-in-time copies 200 _(i) for a source storage 204at different points-in-time, such as at scheduled time intervals.

FIG. 3 illustrates an instance of a log entry 300 _(i) in the logstorage 300 for point-in-time data copied from the source storage 204for one of a plurality of point-in-time copies of the source storage204, and may include: a log entry identifier (ID) 302 providing a uniqueidentifier of the entry in the log storage 300; a point-in-time copyidentifier 302 of the point-in-time copy 200 _(i) for which thepoint-in-time data is intended, which may comprise the point-in-timecopy ID 202; a source storage 306, e.g., volume, and source storagelocation 308, e.g., track in the volume 306, from which thepoint-in-time data was copied; and the point-in-time data 310. In thisway, the log entry 300 _(i) may include metadata on the point-in-timedata as well as the actual data 310. Alternatively, the point-in-timedata 310 may include a pointer to the data

In described embodiments, the log storage 300 sequentially storespoint-in-time data from multiple point-in-time copies to optimize thestorage of the point-in-time data by consolidating in a log storagelocation the data. Further, consolidating point-in-time data in the logstorage 300 reduces wasted space and allows for the storage of many morepoint-in-time copies than would be possible if a separate volume wasrequired to store the point-in-time data for the point-in-time copies.

FIG. 4 illustrates an embodiment of an instance of a recovery metadataentry 400 _(i) in the recovery metadata 400 added for a point-in-timecopy for use by the recovery manager 122, and includes: an entry ID 402providing a unique identifier of the entry in the recovery metadata 400;a point-in-time copy ID 404 of the point-in-time copy for which therecovery metadata 402 is provided; a point-in-time 406 of thepoint-in-time copy 404; a start location in the log storage 408 at whichpoint-in-time data for the point-in-time copy 404 is written sequential;and an end location in the log storage 410 of the last writtenpoint-in-time data for the point-in-time copy 404. In certainembodiments, all the point-in-time data (log entries 300 _(i)) for apoint-in-time copy 404 are written sequentially from the start location408 through the end location 410. In this way, the recovery metadataentry 400 _(i) for each point-in-time copy identifies where in the logstorage 300 the log entries 300 _(i) of point-in-time data for thepoint-in-time copy 404 are stored.

FIG. 5 illustrates an embodiment of operations performed by the storagecontroller point-in-time copy manager 116 to generate a point-in-timecopy 200 _(i) for a source storage 102, such as one or more volumes 104_(i). The point-in-time copy manager 116 may perform the operations ofFIG. 5 in response to a command from the host point-in-time copy manager112, automatically according to a schedule, or activated by some othermeans. Upon initiating (at block 500) an operation to generate apoint-in-time copy 200 _(i) for an indicated source storage, thepoint-in-time copy manager 116 generates (at block 502) change recordinginformation 210 indicating the tracks in the specified source storage tocopy. The point-in-time copy manager 116 generates (at block 504)point-in-time copy information 200 _(i) indicating the point-in-timecopy identifier 202, the source storage 204, e.g., volume, subject tothe copy, a current point-in-time 208 at which the copy is beingcreated, and the generated change recording information 210.

The point-in-time copy manager 116 adds (at block 506) an entry 400 _(i)to the recovery metadata 400 for the established point-in-copy 200 _(i)time indicating an identifier 402 for the added entry 400 _(i); thepoint-in-time copy identifier 202 of the established point-in-time copy200 _(i) in field 404; the point-in-time 208 of the point-in-time copy200 _(i) in field 406; and set the start log location 408 to the nextlocation in the log storage at which to start copying point-in-time datafor the established point-in-time copy 202, which may comprise thelocation addressed by the log storage pointer 120. The end location 410in the entry 400 _(i-1) preceding the entry being added 400 _(i), i.e.,for the immediately preceding point-in-time copy 200 _(i-1), may be set(at block 508) to indicate the log storage location immediatelypreceding the start location 408 of the new entry 400 _(i) (e.g.,location prior to that addressed by the log storage pointer 120). In analternative embodiment, the end location 410 may be updated whenever anew log entry 300 _(i) is added to the log storage 300. The currentactive point-in-time copy 200 _(i-1) is indicated (at block 510) asinactive in status field 212 to inactivate the current activepoint-in-time copy 200 _(i-1), and the just created point-in-time copy200 _(i) is indicated as active in status field 212 of the newly createdpoint-in-time copy 200 _(i).

With the operations of FIG. 5, when establishing a new point-in-timecopy 200 _(i) an entry is also added to recovery metadata 400 thatprovides information on the point-in-time data in the log storage 300for a point-in-time copy 200 _(i) that may be used during roll-backoperations on the source storage 102. Further, the recovery metadata 400entries are in an order in which the point-in-time copies 200 _(i)identified by the entries 400 _(i) are added. This allows the recoverymetadata 400 to determine the ordering of the point-in-time copiesaccording to their points-in-time that may be selected to roll-back thesource storage 102 volumes 104 _(i) to the point-in-time of one of thepoint-in-time copies 200.

FIG. 6 illustrates an embodiment of operations performed by theoperating system 118, and/or another component, such as thepoint-in-time copy manager 116, to handle a write request to the sourcestorage 102 while there is an active point-in-time copy 200 _(i). Uponreceiving (a block 600) a write from a host 106 to one of the tracks inan extent 110 to update data, the operating system 118 determines (atblock 602) whether the target storage 206 for the active point-in-timecopy 200 _(i) is a log storage 300 or a target storage, such as arecovery volume 130 or other target volume. If (at block 602) the targetstorage 206 is the log storage 300, then the operating system 118creates (at block 604) a log entry 300 _(i) for the received writeindicating an identifier 302 of the created entry the point-in-time copyID 304 of the active point-in-time copy 200 _(i), the source storage306, the source storage location 308 that is being updated in the sourcestorage 308, and the point-in-time data 310 for the source location towhich the write is directed. The created log entry 300 _(i) is written(at block 606) to the log storage 300 at a next sequential log storagelocation, such as identified by the log storage pointer 120. Theoperating system 118 updates (at block 608) the log storage pointer 120to point to a next sequential storage location following the storagelocation at which the created log entry 300 _(i) is written. Thereceived write is then applied (at block 610) to the source storagelocation 308 in the source storage 306, as the point-in-time data hasbeen copied to the log storage 300 in a separate target storage 108. Thechange recording information 210 for the point-in-time copy is updated(at block 612) to indicate that the source storage location (e.g.,track) is updated.

If (at block 602) the target storage 206 of the active point-in-timecopy 200 _(i) is not a log storage 300, such as is a recovery volume 130when the active point-in-time copy comprises the recovery point-in-timecopy 200 _(R), then the operating system 118 copies (at block 614) thepoint-in-time data to be overwritten from the source storage 204 to theidentified target storage 206, e.g., recovery volume 130. Control thenproceeds to block 610 to complete the write.

FIG. 7 illustrates an embodiment of operations performed by the recoverymanager 122 to restore the source storage 102, such as a volume 104_(i), to a point-in-time of a point-in-time copy 200 _(i). Uponinitiating (at block 700) an operation to roll-back the source storageto a previous point-in-time, the recovery manager 122 receives (at block702) selection of a point-in-time of one of a selected point-in-timecopies 200 _(S). The recovery manager 122 creates (at block 704) arecovery point-in-time copy 200 _(R) indicating the source storage 204to be rolled-back, a configured recovery volume 130 as the targetstorage 206 (having storage locations corresponding to the sourcestorage 204 locations), a point-in-time 208 comprising the selectedpoint-in-time to restore, change recording information 210 indicatinglocations in the source storage 204 to recover, and having the activestatus 212 to indicate that the recovery point-in-time copy 200 _(R) isactive. A loop of operations is performed at block 706 through 712 foreach point-in-time copy 200 _(i) from the most recent point-in-time copy200 _(N) indicated in the last entry 400 _(N) in the recovery metadata400 through the selected point-in-time copy 200 _(S). For the logentries 300 _(i) from the end location 410 to the start location 408 inthe log storage 300 indicated in the entry 400 _(i) in the recoverymetadata 400 for the point-in-time copy 200 _(i) being processed, therecovery manager 122 sequentially applies (at block 708) thepoint-in-time data from the log entries 300 _(i) to the storagelocations in the recovery volume 130 corresponding to the source storagelocations 308, indicated in the log entries 300 _(i). The changerecording information 210 for the recovery point-in-time copy 200 _(R)is updated (at block 710) to indicate that the source storage locationsof the recovery point-in-time copy 200 _(R), that were written to therecovery volume 130, have been updated. After building the recoveryvolume 130, for the recovery point-in-time copy 200 _(R), with thepoint-in-time data as of the selected point-in-time to restore, therecovery manager 122 may apply (at block 714) the point-in-time data inthe recovery volume 130 to the source storage 306.

With the operations of FIG. 7, the change recording information 210 forthe recovery point-in-time copy 200 _(R) is updated to indicate that thepoint-in-time data for source storage locations written from the logstorage 300 to the recovery volume 130 have been updated. This wouldprevent the operating system 118 from copying point-in-time data to beupdated from the source storage 102 to the recovery volume 130 tooverwrite data copied from the log storage because the change recordinginformation 210 indicates the point-in-time data has already beenapplied as a result of the copying of the point-in-time data from thelog storage 300. This ensures that the point-in-time data from the logstorage 300 written to the recovery volume 130 is not overwritten bypoint-in-time data at the source storage that is subsequently updated.Further, with the operations of FIG. 7, all of the point-in-time data asof the restore point-in-time is staged in the recovery volume 130 beforebeing applied to the source storage 204 of the recovery point-in-timecopy 200 _(R). Once the point-in-time data in the recovery volume 130 isapplied to the source storage 204, the source storage, e.g., volume, isrestored to the recovery point-in-time.

In an alternative embodiment, the point-in-time data from the logstorage 300 may be directly applied to the source storage without usinga recovery point-in-time copy 200 _(R) of the source storage. However,the advantage of the recovery point-in-time copy 200 _(R) is that itallows user access to the source storage 102 to continue while thepoint-in-time data is being recovered.

FIG. 8 illustrates an embodiment of operations performed by the recoverymanager 122 or some other component to iteratively generate recoveryvolumes 130 for different recovery point-in-times to roll back thesource storage 102 to a guessed most current point-in-time in whichthere is valid data in the event the current source storage 102 hasinvalid or corrupt data. Upon initiating (at block 800) operations toiteratively perform roll-back operations to a previous point-in-timehaving valid data, the recovery manager 122 sets (at block 802) a lastinvalid point-in-time copy to the point-in-time copy 404 in the last(most recent) entry 400 _(N) in the recovery metadata 400 and a lastvalid point-in-time copy to the point-in-time copy 404 in the first oroldest entry 400 ₁ in the recovery metadata 400, where there are Nentries in the recovery metadata 400.

The recover manager 122 selects (at block 804) a recovery point-in-timeas a point-in-time of a point-in-time copy between the last valid andlast invalid point-in-time copies. The recover manager 122 performs (atblock 806) operations at blocks 704-712 in FIG. 7 to generate a recoverypoint-in-time copy 200 _(R) and recovery volume 130 for the selectedrecovery point-in-time. The recovery manager 122 may process (at block808) the recovery volume 130 point-in-time data along with unchangeddata in the source storage 102 to determine if the recovery volume 130has valid data, or is not corrupt. Error correction and data validationalgorithms known in the art may be used to determine whether therecovery volume 130 is valid or corrupt. To perform further iterationsto estimate the point-in-time copy having the most current valid data,the recovery manager 122 may perform the operations at block 810 et seq.

If (at block 810) the recovery volume 130 has valid data, then the lastvalid point-in-time copy is set (at block 812) to the point-in-time copy200 _(i) for the selected recovery point-in-time. The recovery manager122 determines (at block 814) whether there any entries 400 _(i) betweenthe entries for the last valid and last invalid point-in-time copies inthe recovery metadata 400. If (at block 814) there are further potentialvalid entries to consider, then control proceeds back to block 804 toselect a further recovery point-in-time to use to perform anotheriteration to restore the volume 130. If (at block 814) there are nofurther entries between the entries for the last valid and last invalidpoint-in-time copies in the recovery metadata 400, then the recoverymanager 122 applies (at block 816) the recently created recovery volume130 for the last valid point-in-time copy to the source storage 102 toroll back the source storage 102 to the last valid point-in-time copy200 _(i).

If (at block 810) the recovery volume 130 has invalid data, then thelast invalid point-in-time copy is set (at block 818) to thepoint-in-time copy 200 _(i) for the selected recovery point-in-time andcontrol proceeds back to block 804 to select a recovery point-in-time touse to perform another iteration to restore the volume 130.

With the operations of FIG. 8, numerous point-in-time copies may beiteratively recovered in a recovery volume 130 to determine apoint-in-time copy for a most current point-in-time having valid data.In alternative embodiments, other operations may be used to estimate themost current point-in-time copy, such as performing the iterativeoperations of FIG. 8 for a limited number of times before selecting thelast valid point-on-time copy to use for the roll-back operation.Alternatively, other selection techniques may be used to select one ofthe point-in-time copies to use to roll-back the source storage 102 to apoint where there is valid data.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++ or the like,and conventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The computational components of FIG. 1, including the storage controller100 and host 106 may be implemented in one or more computer systems,such as the computer system 902 shown in FIG. 9. Computer system/server902 may be described in the general context of computer systemexecutable instructions, such as program modules, being executed by acomputer system. Generally, program modules may include routines,programs, objects, components, logic, data structures, and so on thatperform particular tasks or implement particular abstract data types.Computer system/server 902 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 9, the computer system/server 902 is shown in the formof a general-purpose computing device. The components of computersystem/server 902 may include, but are not limited to, one or moreprocessors or processing units 904, a system memory 906, and a bus 908that couples various system components including system memory 906 toprocessor 904. Bus 908 represents one or more of any of several types ofbus structures, including a memory bus or memory controller, aperipheral bus, an accelerated graphics port, and a processor or localbus using any of a variety of bus architectures. By way of example, andnot limitation, such architectures include Industry StandardArchitecture (ISA) bus, Micro Channel Architecture (MCA) bus, EnhancedISA (EISA) bus, Video Electronics Standards Association (VESA) localbus, and Peripheral Component Interconnects (PCI) bus.

Computer system/server 902 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 902, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 906 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 910 and/or cachememory 912. Computer system/server 902 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 913 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 908 by one or more datamedia interfaces. As will be further depicted and described below,memory 906 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 914, having a set (at least one) of program modules 916,may be stored in memory 906 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. The components of the computer 902 may be implemented asprogram modules 916 which generally carry out the functions and/ormethodologies of embodiments of the invention as described herein. Thesystems of FIG. 1 may be implemented in one or more computer systems902, where if they are implemented in multiple computer systems 902,then the computer systems may communicate over a network.

Computer system/server 902 may also communicate with one or moreexternal devices 918 such as a keyboard, a pointing device, a display920, etc.; one or more devices that enable a user to interact withcomputer system/server 902; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 902 to communicate withone or more other computing devices. Such communication can occur viaInput/Output (I/O) interfaces 922. Still yet, computer system/server 902can communicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 924. As depicted, network adapter 924communicates with the other components of computer system/server 902 viabus 908. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 902. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

The terms “an embodiment”, “embodiment”, “embodiments”, “theembodiment”, “the embodiments”, “one or more embodiments”, “someembodiments”, and “one embodiment” mean “one or more (but not all)embodiments of the present invention(s)” unless expressly specifiedotherwise.

The terms “including”, “comprising”, “having” and variations thereofmean “including but not limited to”, unless expressly specifiedotherwise.

The enumerated listing of items does not imply that any or all of theitems are mutually exclusive, unless expressly specified otherwise.

The terms “a”, “an” and “the” mean “one or more”, unless expresslyspecified otherwise.

Devices that are in communication with each other need not be incontinuous communication with each other, unless expressly specifiedotherwise. In addition, devices that are in communication with eachother may communicate directly or indirectly through one or moreintermediaries.

A description of an embodiment with several components in communicationwith each other does not imply that all such components are required. Onthe contrary a variety of optional components are described toillustrate the wide variety of possible embodiments of the presentinvention.

When a single device or article is described herein, it will be readilyapparent that more than one device/article (whether or not theycooperate) may be used in place of a single device/article. Similarly,where more than one device or article is described herein (whether ornot they cooperate), it will be readily apparent that a singledevice/article may be used in place of the more than one device orarticle or a different number of devices/articles may be used instead ofthe shown number of devices or programs. The functionality and/or thefeatures of a device may be alternatively embodied by one or more otherdevices which are not explicitly described as having suchfunctionality/features. Thus, other embodiments of the present inventionneed not include the device itself.

The foregoing description of various embodiments of the invention hasbeen presented for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Many modifications and variations are possible in lightof the above teaching. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto. The above specification, examples and data provide acomplete description of the manufacture and use of the composition ofthe invention. Since many embodiments of the invention can be madewithout departing from the spirit and scope of the invention, theinvention resides in the claims herein after appended.

1-23. (canceled)
 24. A computer program product for managingpoint-in-time copies of a source storage, wherein the computer programproduct comprises a computer readable storage medium having programinstructions embodied therewith, the program instructions executable bya processor to cause operations, the operations comprising: storingpoint-in-time data for multiple point-in-time copies of a source storagein a log storage; receiving a write to the source storage having anactive point-in-time copy; copying point-in-time data in the sourcestorage to be overwritten by the received write to the log storage; andso using the log storage to roll-back the source storage to a selectedpoint-in-time of one of the point-in-time copies.
 25. The computerprogram product of claim 24, wherein the operations further comprise:determining whether point-in-time copy information for the sourcestorage indicates a target storage or the log storage for thepoint-in-time data, wherein the point-in-time data is copied to thesource storage in response to determining that the point-in-time copyinformation indicates the log storage for the point-in-time data; andcopying the point-in-time data to the target storage in response todetermining that the point-in-time copy information indicates the targetstorage for the point-in-time data.
 26. The computer program product ofclaim 24, wherein the point-in-time data is written to the log storageat sequential storage locations in an order in which the point-in-timedata was updated at the source storage.
 27. The computer program productof claim 24, wherein the operations further comprise: for each of thepoint-in-time copies, maintaining recovery metadata indicating locationsin the log storage having point-in-time data for a point-in-time copy,wherein the using the log storage to roll-back the source storagecomprises copying the point-in-time data to the source storage from afirst location through a last location in the log storage indicated inthe recovery metadata for the selected point-in-time to roll-back thesource storage.
 28. The computer program product of claim 24, whereinthe selected point-in-time is for a previous point-in-time, whereinusing the log storage to roll-back the source storage to the previouspoint-in-time comprises: copying, to a recovery storage, thepoint-in-time data in the log storage from a most recent point-in-timecopy to the selected point-in-time copy in sequential reverse order. 29.The computer program product of claim 28, wherein the operations furthercomprise: indicating, in a change recording data structure, that storagelocations in the recovery storage to which the point-in-time data wasapplied have been updated.
 30. The computer program product of claim 24,wherein the operations further comprise: iteratively creating recoverypoint-in-time copies of the source storage for recovery point-in-timesby applying, to a recovery storage for each of the recoverypoint-in-time copies, the point-in-time data in the log storage frompoint-in-time copies for points-in-time greater than and equal to one ofthe recovery point-in-times to determine one of the recoverypoint-in-time copies having valid data in the recovery storage as of adetermined recovery point-in-time between two recovery point-in-timecopies having invalid data; and applying the point-in-time data from therecovery storage for the determined recovery point-in-time copies to thesource storage to return to the determined recovery point-in-time atwhich the source storage had valid data.
 31. A system for managingpoint-in-time copies of a source storage, comprising: processor; and acomputer readable storage medium having program instructions embodiedtherewith, the program instructions executable by a processor to causeoperations, the operations comprising: storing point-in-time data formultiple point-in-time copies of a source storage in a log storage;receiving a write to the source storage having an active point-in-timecopy; copying point-in-time data in the source storage to be overwrittenby the received write to the log storage; and so using the log storageto roll-back the source storage to a selected point-in-time of one ofthe point-in-time copies.
 32. The system of claim 31, wherein theoperations further comprise: determining whether point-in-time copyinformation for the source storage indicates a target storage or the logstorage for the point-in-time data, wherein the point-in-time data iscopied to the source storage in response to determining that thepoint-in-time copy information indicates the log storage for thepoint-in-time data; and copying the point-in-time data to the targetstorage in response to determining that the point-in-time copyinformation indicates the target storage for the point-in-time data. 33.The system of claim 31, wherein the point-in-time data is written to thelog storage at sequential storage locations in an order in which thepoint-in-time data was updated at the source storage.
 34. The system ofclaim 31, wherein the operations further comprise: for each of thepoint-in-time copies, maintaining recovery metadata indicating locationsin the log storage having point-in-time data for a point-in-time copy,wherein the using the log storage to roll-back the source storagecomprises copying the point-in-time data to the source storage from afirst location through a last location in the log storage indicated inthe recovery metadata for the selected point-in-time to roll-back thesource storage.
 35. The system of claim 31, wherein the selectedpoint-in-time is for a previous point-in-time, wherein using the logstorage to roll-back the source storage to the previous point-in-timecomprises: copying, to a recovery storage, the point-in-time data in thelog storage from a most recent point-in-time copy to the selectedpoint-in-time copy in sequential reverse order.
 36. The system of claim35, wherein the operations further comprise: indicating, in a changerecording data structure, that storage locations in the recovery storageto which the point-in-time data was applied have been updated.
 37. Thesystem of claim 31, wherein the operations further comprise: iterativelycreating recovery point-in-time copies of the source storage forrecovery point-in-times by applying, to a recovery storage for each ofthe recovery point-in-time copies, the point-in-time data in the logstorage from point-in-time copies for points-in-time greater than andequal to one of the recovery point-in-times to determine one of therecovery point-in-time copies having valid data in the recovery storageas of a determined recovery point-in-time between two recoverypoint-in-time copies having invalid data; and applying the point-in-timedata from the recovery storage for the determined recovery point-in-timecopies to the source storage to return to the determined recoverypoint-in-time at which the source storage had valid data.
 38. A methodfor managing point-in-time copies of a source storage, comprising:storing point-in-time data for multiple point-in-time copies of a sourcestorage in a log storage; receiving a write to the source storage havingan active point-in-time copy; copying point-in-time data in the sourcestorage to be overwritten by the received write to the log storage; andso using the log storage to roll-back the source storage to a selectedpoint-in-time of one of the point-in-time copies.
 39. The method ofclaim 38, further comprising: determining whether point-in-time copyinformation for the source storage indicates a target storage or the logstorage for the point-in-time data, wherein the point-in-time data iscopied to the source storage in response to determining that thepoint-in-time copy information indicates the log storage for thepoint-in-time data; and copying the point-in-time data to the targetstorage in response to determining that the point-in-time copyinformation indicates the target storage for the point-in-time data. 40.The method of claim 38, further comprising, wherein the point-in-timedata is written to the log storage at sequential storage locations in anorder in which the point-in-time data was updated at the source storage.41. The method of claim 38, further comprising, further comprising: foreach of the point-in-time copies, maintaining recovery metadataindicating locations in the log storage having point-in-time data for apoint-in-time copy, wherein the using the log storage to roll-back thesource storage comprises copying the point-in-time data to the sourcestorage from a first location through a last location in the log storageindicated in the recovery metadata for the selected point-in-time toroll-back the source storage.
 42. The method of claim 38, furthercomprising wherein the selected point-in-time is for a previouspoint-in-time, wherein using the log storage to roll-back the sourcestorage to the previous point-in-time comprises: copying, to a recoverystorage, the point-in-time data in the log storage from a most recentpoint-in-time copy to the selected point-in-time copy in sequentialreverse order.
 43. The method of claim 42, further comprising:indicating, in a change recording data structure, that storage locationsin the recovery storage to which the point-in-time data was applied havebeen updated.